Faslane

Some of the century's biggest civil engineering challenges came from the development of maintenance facilities for nuclear submarines in the late 1980s and early 1990s. Construction of nuclear submarine facilities at Faslane in Scotland produced two major projects which between them rivalled the Channel Tunnel in size and complexity.

Here, Costain/Taylor Woodrow built a huge floating concrete explosives- handling jetty. Designed by consultant Rendel Palmer & Tritton, the 200m long, 80m wide, 47m deep precast structure was bigger than aircraft carrier HMS Invincible. It had to float rather than rest on piles in deep water, just off the steep sided Gareloch shoreline.

Costain/Taylor Woodrow cast the U-shaped jetty at Hunterston, 38km from Faslane, before towing it into position. It was fixed to the shore with two pairs of mooring booms and a huge steel brace was fixed beneath the open end of the jetty to give it extra rigidity.

At Faslane, Trafalgar House built the ship lift for raising 16,000t submarines out of the water for maintenance. The lift platform was built over the loch, on 821 tubular steel piles up to 50m long and driven into bedrock in water between 22m and 30m deep. Some of the piles were also raked for extra lateral stability.

Piling tolerances were very tight because design criteria for nuclear submarine facilities said they should withstand an earthquake measuring six on the Richter scale. This created problems for piling specialist Cementation which hit unpredictable ground in the boulder clay on the loch bed. It had to extract and replace 70 piles after they had been thrown off line.

The Public Accounts Committee criticised the Ministry of Defence and the Property Services Agency for mismanaging the project. It said that cost overran by £800M as a result of poor project management by the MoD and PSA, inflation, design changes during construction and difficulties meeting earthquake design codes. But even though the final cost of the two facilities emerged at £1.7bn - double original estimates - the two projects are widely held to be major civil engineering achievements, given their size and design constraints.

'I remember them as very glamorous days,' said the then Trafalgar House operations director Peter Jeffries, when the shiplift opened in 1993. 'We were working 24 hours a day, the site looked tremendous and the noise and smell were overwhelming. It was a very exciting time.'

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